With the development and industrialization of the new generation wireless broadband communication technology, handheld multi-media terminals mainly including PDAs (Personal Digital Assistant), multi-media phones and tablets are widely used, expected to become a unified platform for the popularization and application of the information technology which can support variety of information application and develop rapidly in various fields such as industry, agriculture, medical, education, family and personal communication. High speed data transmission is one of the key technologies for fast development and wide application of the handheld multi-media terminals.
In order to ensure effective high quality image data or even video data transmission during the data exchange between the terminals, sufficient data rate is required. However, the improvement of the data rate not only challenges the performance of the whole receiver of the terminal such as sensitivity and noise, but also tests the power consumption of the analog baseband amplifiers and filters. Furthermore, the high data rate also affects the spectrum planning of the system.
Nowadays, impulse radio ultra wide bandwidth (IR-UWB) system is one of an international mainstream transceiver system to realize the new generation wireless broadband communication technology. The ultra wide bandwidth (UWB) system has been clearly defined by the FCC (Federal Communications Commission) as early as February 2002 to operate in the 3.1 to 10.6 GHz frequency range at the power spectral density lower than −41.3 dBm/MHz with a −10 dB fractional bandwidth (absolute bandwidth to center frequency ratio) of more than 20% or a −10 dB absolute bandwidth of more than 500 MHz. Accordingly, the UWB technology uses a remarkably wider band than all the conventional communication technology.
Researchers have proposed a system to achieve the ultra wide bandwidth communication under the UWB framework—an impulse radio ultra wide bandwidth (IR-UWB) system. The core of the IR-UWB concept is that the use of extremely short pulses in the time domain causes a corresponding broad frequency spectrum in the frequency domain. In other words, the extremely short duration impulse radio transferred by the communication system in the time domain, which is a signal of very small duty ratio in a cycle transmitted by the communication system, generates a wide bandwidth signal in the frequency domain through the Fourier transform. When the bandwidth of the generated signal exceeds 500 MHz, the signal becomes a standard UWB signal and the transmission protocol thereof complies with the UWB regulation.
At present, OOK modulation is the most common signal modulation scheme applied in the IR-UWB system. According to the OOK modulation, if there exists an impulse radio signal with a frequency f during a unit time period (such as T seconds), binary data “1” will be transmitted during the unit time period (such as T seconds); and if there exists no signals during the unit time period (such as T seconds), binary data “0” will be transmitted, as shown in FIG. 1. Therefore, only one binary data can be transmitted during a unit time period, which results in a low utilization of time. The time interval T generally ranges from 0.1 us to 10 us and is preferably to be 1 us. Specifically, if the unit time period T is assumed to be 1 us and the impulse radio signal transmitted during the unit time period has only one frequency, the data rate of the whole impulse-radio system will be 1 MHz.
However, how to effectively utilize the IR-UWB system to increase the data transfer rate has become an important topic in the IR-UWB system nowadays. It is noted that although researchers have taken a plurality of measurements including circuit and system design to improve the data rate by 20-30%, the complexity of the circuit greatly arises and the power consumption of the system sharply increases.